1. Field of the Invention
The present invention relates to a multilayer electronic device reducing the equivalent serial inductance (ESL) and able to be used as a capacitor array and a method for producing the same, more particularly relates to a multiterminal multilayer capacitor and a method for producing the same.
2. Description of the Related Art
In the past, capacitors have been made wide use of as types of electronic devices. Multilayer ceramic capacitors are also being used in power supply circuits of LSIs.
On the other hand, in a power supply circuit of a CPU or other LSI in which the capacitor shown in FIG. 10 is arranged, sharp fluctuations in current sometimes occur at the time of operation of the LSI. Along with the fluctuations in current, the voltage of the power supply circuit widely fluctuates due to the inductance (L) and resistance (R) of the interconnections and the ESL and equivalent serial resistance (ESR) of the capacitor, so that the operation of the LSI is sometimes hampered.
Therefore, in the past, in a power supply circuit of an LSI, a capacitor with a low ESL has been used to suppress fluctuations in voltage accompanying sharp fluctuations in current and to thereby stabilize the power supply circuit.
In particular, recent CPUs have been required to be reduced further in ESL since operating frequencies and currents have been made higher along with higher operating speeds. Therefore, in multiterminal capacitors, one example of a multilayer ceramic chip capacitor, the directions of the currents have been controlled to become opposite between the nearby terminal electrodes.
As shown in Japanese Unexamined Patent Publication (Kokai) No. 9-17693, Japanese Unexamined Patent Publication (Kokai) No. 11-144996, U.S. Pat. No. 5,880,925, etc., the main part of a conventional reduced ESL multiterminal capacitor is comprised of a rectangular parallelopiped body configured by a plurality of internal electrodes superposed via ceramic layers so as to give an electrostatic capacity by the ceramic layers forming the body.
Further, each of these internal electrodes has two leads each led out to two or more side faces among the four side faces of the body.
Terminal electrodes connected to these leads are attached to these side faces. Note that voltages are supplied with alternatingly opposite polarities to the nearby terminal electrodes connected to the leads of the nearby internal electrodes in the stacking direction. Since the polarities of the voltages supplied to the nearby leads differ, the magnetic fluxes generated due to the high frequency currents flowing from the terminal electrodes are canceled out between these adjoining leads and therefore the ESL is reduced.
On the other hand, the stabilization of a power supply circuit depends to a large extent on the ESR of the capacitor as well. In a conventional reduced ESL capacitor, since, as mentioned above, the electrical resistance becomes smaller along with the provision of the plurality of leads. As a result, the ESR becomes extremely small, therefore the power supply circuit using such a capacitor lacked stability.
That is, the conventional reduced ESL capacitor had an extremely small ESR, so when resonance was caused due to inductance of the peripheral circuits, the voltage dropped sharply or ringing or other attenuation vibration easily occurred.
On the other hand, along with the increasing integration of circuits, capacitors etc. for power supply circuits are now being required to be a single capacitor comprised of a plurality of component capacitors giving electrostatic capacities differing in accordance with a plurality of circuits.
Further, along with the increasing integration of circuits, capacitors etc. for power supply circuits have been required to be a single capacitor comprised of a plurality of internal electrodes, but if fabricating internal electrodes differing in pattern of leads along with the number of internal electrodes, the production process is liable to become complicated and the manufacturing costs increase.
A first object of the present invention is to provide a multilayer electronic device and method of producing a multilayer electronic device not only able to prevent the ESR from becoming extremely small while reducing the ESL, but also enabling the manufacturing costs to be reduced.
A second object of the present invention is to provide a multilayer electronic device able to reduce the ESL and able to be used as a capacitor array or composite electronic device etc.
To achieve the object, a first multilayer electronic device of the present invention is comprised of a capacitor body formed by stacking dielectric layers; a plurality of internal electrodes separated by dielectric layers inside the capacitor body, each having at least one lead led out toward any side face of the capacitor body, and differing in position of arrangement of the leads with the nearby internal electrodes; and a plurality of terminal electrodes arranged at the outside surface of the capacitor body and connected to any of the plurality of internal electrodes through the leads; wherein the internal electrodes being divided into blocks of electrode patterns of a plurality of internal electrodes adjoining each other via the dielectric layers, and the electrode patterns of the internal electrodes belonging to the different blocks being the same in the shapes of the electrode patterns, but different in rotational positions about an axis perpendicular to the planes of the electrode patterns.
As a result, when supplying a current to the multilayer electronic device, the plurality of internal electrodes of each blocks connected to the outside circuits via the leads constitute electrodes arranged in parallel while facing each other to form capacitors.
According to the first multilayer electronic device of the present invention, since the leads are led out from the internal electrodes toward the side faces of the capacitor body, positive and negative currents are supplied in opposite directions to the nearby leads to cancel the magnetic fluxes. Therefore, the parasitic inductance of the multilayer electronic device itself can be reduced and the ESL is reduced.
On the other hand, by having just a single lead be led out from the portion of the internal electrode giving the electrostatic capacity and connected to a terminal electrode, it is possible to supply current concentratedly to this single lead and to increase the electrical resistance at the lead. As a result of the increase in the electrical resistance at the lead in this way, even if ESL reduction technology is adopted for supplying positive and negative currents in opposite directions between the nearby leads and canceling out the magnetic fluxes is adopted, the ESR can be prevented from becoming overly small.
Further, according to the first multilayer electronic device of the present invention, by stacking a plurality of blocks of the same repeating electrode pattern structure changed only in rotational position, there is no longer a need to fabricate internal electrodes with different lead patterns to match the number of internal electrodes, so that the production process is simplified and the manufacturing costs reduced.
Still further, according to the first multilayer electronic device of the present invention, it is also possible to incorporate a plurality of capacitors into a single multilayer electronic device. Therefore, by reducing the number of multilayer electronic devices to be mounted in an electrical product, the manufacturing costs can be reduced and, along with the increased integration of circuits, the required space can be reduced.
In the first electronic device of the present invention, preferably the capacitor body is shaped as a hexagon and the plurality of terminal electrodes are arranged at each of at least two side faces among the four side faces of the hexagonal capacitor body.
In this case, since the capacitor body is formed in a hexagonal shapexe2x80x94the easiest to manufacture as a multilayer electronic devicexe2x80x94, production becomes easy. Further, since the plurality of terminal electrodes are provided at least at two side faces among the four side faces of the hexagonal capacitor body, when supplying high frequency currents to the terminal electrodes so that the terminal electrodes of the side faces alternately become positive and negative, positive and negative currents flow in opposite directions at the nearby leads. Therefore, the effect of cancellation of the magnetic flux occurs concentratedly at these side faces and the ESL is reduced more.
In the first electronic device of the present invention, preferably the terminal electrodes adjoining each other at the same side face where a plurality of terminal electrodes are provided are connected to the different internal electrodes.
In this case, by having currents flow so that the polarities of the nearby terminal electrodes become different, the magnetic fluxes generated at the leads are canceled out due to the currents flowing in the leads in opposite directions and the effect of reduction of the ESL appears even more reliably.
In the first electronic device of the present invention, preferably the capacitor body is shaped as a hexagon and the plurality of terminal electrodes are arranged at each of the four side faces of the hexagonal capacitor body.
In this case, when supplying high frequency currents to the terminal electrodes so that the terminal electrodes of the side faces become alternately positive and negative, the effect of supplying positive and negative currents in opposite directions between the nearby leads to cancel out the magnetic fluxes occurs at the four side faces and the ESL is further reduced. Further, since the terminal electrodes are arranged at the four side faces of the hexagonal shape, it is possible to make a four block stack by changing the rotational positions of four blocks respectively having a plurality of internal electrodes, so that the production process can be simplified and a multilayer electronic device having the plurality of internal electrodes can be obtained.
The method of producing a multilayer electronic device of the present invention comprises the steps of forming on a dielectric layer an internal electrode of a pattern with at least one lead led out; stacking the dielectric layers on which the internal electrodes of patterns different from each other are formed to prepare blocks respectively having a plurality of the same repeating electrode patterns; and stacking a plurality of the blocks in a state where the plurality of blocks are rotated about an axis orthogonal to the planes of the internal electrodes so that the blocks adjoining each other in the stacking direction are at mutually different rotational positions so as to form a capacitor body.
According to the method of production of the present invention, since the plurality of internal electrodes are made the block, the plurality of blocks are rotated about the axis orthogonal to the planes formed by the internal electrodes to different rotational positions, and the blocks are stacked in that state, even in a multilayer electronic device of a structure having a plurality of internal electrodes, the production process is simplified and the manufacturing costs are reduced.
The method of production of the present invention preferably further comprises, when stacking the plurality of blocks to form the capacitor body, forming the capacitor body in a hexagonal shape, arranging a plurality of terminal electrodes at each of the four side faces of the hexagonal capacitor body, and connecting the terminal electrodes to any of the internal electrodes through the leads.
To achieve the second object, the second multilayer electronic device of the present invention comprises a capacitor body formed by stacking dielectric layers; four internal electrodes each having leads led out toward two opposite side faces of the capacitor body and arranged separated by dielectric layers inside the capacitor body in a state with patterns of the leads differing from each other; and four pairs of terminal electrodes arranged outside the capacitor body and connected to any of the four internal electrodes through the leads.
According to the second multilayer electronic device of the present invention, since the leads are led out to two facing side faces of the capacitor body, currents flow straight by short routes at the time of carrying a current and the positive and negative currents intersect two-dimensionally to cancel out the magnetic fluxes among the four internal electrodes in the multilayer electronic device. As a result, the parasitic inductance of the multilayer electronic device itself is sharply reduced and the ESL is reduced.
Further, since an electrostatic capacity is obtained among the four internal electrodes, by using these divided into two internal electrodes each, it is also possible to use the device as a capacitor array or composite electronic device.
In the second electronic device of the present invention, preferably the capacitor body is shaped as a hexagon, the terminal electrodes are provided at each of the four side faces of the hexagonal capacitor body, and the two opposite side faces and the two opposite side faces positioned rotated 90 degrees from these two side faces have terminal electrode array structures able to be used as independent capacitors.
In this case, since terminal electrodes are provided at the four side faces of the hexagonal capacitor body, not only do the routes over which the currents flow become the shortest, but also, when supplying high frequency currents to the terminal electrodes so that the terminal electrodes of the side faces alternately become positive and negative, the currents intersect when flowing from the terminal electrodes of the four side faces to the internal electrodes along with the four internal electrodes connected to the terminal electrodes becoming positive and negative polarities and as a result the parasitic inductance further falls.
In the second electronic device of the present invention, preferably the terminal electrodes are arranged at the side faces of the capacitor body so that the nearby terminal electrodes are connected to mutually the different internal electrodes.
In this case, currents flow so that the polarities of the nearby terminal electrodes become different and the magnetic fluxes generated are canceled out by the high frequency currents flowing in the internal electrodes in opposite directions, so that the parasitic inductance further falls.
In the second electronic device of the present invention, preferably the internal electrodes, including leads, having mutually different electrode patterns of internal electrodes and stacked via the dielectric layers form a block and a plurality of blocks are arranged stacked and superposed to constitute the capacitor body.
In this case, it becomes easy to divide the internal electrodes into groups of pluralities of internal electrodes for use and possible to design capacitor arrays or composite electronic devices more reliably. Further, it becomes possible to use the same electrode patterns for every blocks. Even if the number of internal electrodes stacked is increased, there is no longer a need to increase the number of patterns and the production process becomes easy, which contributes to the reduction of the manufacturing costs.
In the second electronic device of the present invention, preferably a plurality of the leads are respectively led out from each internal electrode to each side face.
In this case, since the leads are provided plurally, the effect of cancellation of the magnetic flux by the intersection of the positive and negative currents two-dimensionally is enhanced.
To achieve the second object, a third multilayer electronic device of the present invention comprises a capacitor body formed by stacking dielectric layers; four internal electrodes separated by dielectric layers inside the capacitor body and each having leads led out toward three side faces of the capacitor body; and a plurality of terminal electrodes arranged at an outside surface of the capacitor body and connected to any of the four internal electrodes through the leads.
According to the third multilayer electronic device of the present invention, since the leads are led out toward three side faces of the capacitor body, the space surrounding the internal electrodes can be used more effectively than internal electrodes of a multilayer capacitor with leads led out in two directions and currents flow over straight, short routes when supplying a current. Further, by having positive and negative currents intersect more two-dimensionally to cancel out the magnetic fluxes in the four internal electrodes in the multilayer electronic device, the parasitic inductance of the multilayer electronic device itself is sharply reduced. Therefore, the ESL is reduced.
In the third electronic device of the present invention, preferably the capacitor body is shaped as a hexagon and the terminal electrodes are provided at each of the four side faces of the hexagonal capacitor body.
In this case, since internal electrodes are provided at the four side faces of the hexagonal capacitor body, it is possible to make maximum use of the space surrounding the capacitor body and the routes over which the currents flow become the shortest. Further, when supplying high frequency currents to the terminal electrodes so that the terminal electrodes of the side faces alternately become positive and negative, the four internal electrodes connected to the terminal electrodes becoming positive and negative polarities, currents intersect when flowing from the terminal electrodes of the four side faces to the internal electrodes, and, as a result, the parasitic inductance further falls.
In the third electronic device of the present invention, preferably the terminal electrodes are arranged at the side faces of the capacitor body so that the nearby terminal electrodes are connected to mutually the different internal electrodes.
In this case, currents flow so that the polarities of the the nearby terminal electrodes become different and the magnetic fluxes generated are canceled by the high frequency currents flowing in the internal electrodes in opposite directions, so that the parasitic inductance further falls.
In the third electronic device of the present invention, preferably patterns of the leads of the four internal electrodes differ from one another, and the leads which are led out from two internal electrodes separated via one internal electrode to the two opposite side faces are respectively connected to the same terminal electrodes.
In this case, the parasitic inductance can be reduced while effectively reducing the number of terminal electrodes.
In the third electronic device of the present invention, preferably the internal electrodes, including leads, having mutually different electrode patterns of the internal electrodes and stacked via the dielectric layers form a block and a plurality of blocks are arranged stacked and superposed to constitute the capacitor body.
In this case, it becomes easy to divide the internal electrodes into groups of pluralities of internal electrodes for use and possible to design capacitor arrays or composite electronic devices more reliably. Further, it becomes possible to use the same electrode patterns for every blocks. Even if the number of internal electrodes stacked is increased, there is no longer a need to increase the number of patterns and the production process becomes easy, which contributes to the reduction of the manufacturing costs.